1. Field of the Invention
This invention lies in the field of pulse dampers for reciprocating pumps.
2. Description of the Prior Art
Certain laboratory systems, prominent among which are high-performance liquid chromatography (HPLC) systems, require a continuous and steady flow of liquid. In HPLC, the continuous and steady flow assures that the chromatogram for any given sample will be readily readable and sufficiently standardized so that components can be identified by their retention times, properly quantified if desired, and generally reproducible. A dual-headed reciprocating pump system is often used to produce the flow, and a common example of such a system is one with two pump chambers, each with its own piston but with the pistons coordinated by a common motor to drive the pistons in alternating manner. A common problem with dual-headed reciprocating systems is the occurrence of pressure pulsations that occur when the system switches over from one piston to the other. Pressure pulsations cause pulsations in the output flow, and hence the flow rate of the output flow, from the system. When the liquid is a mixture formed by combining two liquids of different compositions either outside of or within the pump chambers, the resulting mixture will often contain ripples in its composition, i.e., fluctuations in the proportion of one liquid relative to the other downstream of the mixing site, in addition to pressure pulsations. Composition ripples occur at elevated pumping pressures and are the result of compression and decompression of the fluid in each pump at the beginning and end of each stroke, respectively. Dampers can be added to individual pumps to dampen the pressure pulsations, but the composition ripples often remain.